As the track density of an HDD increases in recent years, the problem of interference with an adjacent track is becoming serious. In particular, reducing side write due to the recording head magnetic field fringe effect is an important technical subject. A discrete track pattern medium (DTR medium) in which recording tracks are physically separated can reduce the side erase phenomenon that occurs during recording and the side read phenomenon by which information of an adjacent track mixes in during reproduction, thereby increasing the density is the cross track direction. This makes the DTR medium promising as a high-density magnetic recording medium. In addition, a bit patterned medium (BPM) physically divided in the bit direction as well has been proposed as a high-density magnetic recording medium capable of suppressing the medium noise and the thermal decay phenomenon by which recorded data disappears at room temperature.
Since the DTR medium and BPM are manufactured using the etching processing technique, the manufacturing cost may increase. Therefore, the following method has been proposed. That is, fine patterns obtained by EB (Electron Beam) lithography are transferred to a master, and a mother stamper (or a master stamper) such as a Ni stamper is duplicated from the master by electroforming. The mother stamper is then set in an injection molding machine, and resin stampers are mass-produced by injection molding. The DTR medium or BPM manufactured by UV (UltraViolet-curing) imprinting using the resin stamper.
When manufacturing the DTR medium or BPM, it is necessary to transfer fine patterns whose size is 1/10 or less that of patterns formed on optical disks. When patterns are downsized as the recording density increases, however, it often becomes difficult to duplicate the mother stamper from the master by electroforming.
For example, when a conductive film for performing electroforming is deposited by sputtering, the openings of fine patterns are closed to form cavities because the deposition rate of pattern projections is higher than that pattern recesses. Since no electroformed film is formed in master recesses, pattern transfer defects sometimes occur. When performing deposition by a chemical vapor growth method, such as a transfer method capable of depositing layers even on the sidewalls by using CVD or ALD, a conductive layer can be deposited even in pattern recesses without forming cavities. However, in a deposition method using a chemical reaction in a vapor phase, a master (or Ni stamper) and conductive layer come in tight contact with each other. This sometimes makes it impossible to clearly release patterns.
As described above, as patterns are downsized, conductive film deposition defects occur in pattern recesses when using a physical vapor growth method such as sputtering, and release defects occur when using a chemical vapor growth method such as CVD or ALD. This makes it difficult to simultaneously achieve the conductivity, releasability, and pattern reproducibility when duplicating fine patterns.